"It won't be immediately as we have to let the swelling come down. It's a blow."

The Serbian’s return from a calf problem sustained in the opening-day win at West Brom was cited by many as the moment Manchester United’s defensive difficulties began to ease.

Despite repeated suggestions the player would leave Old Trafford, Vidic remains one of the key figures in Ferguson’s squad and his absence will place additional focus on younger players such as Phil Jones and Chris Smalling, who were chided by Roy Keane in Switzerland last night.

It will certainly cause Ferguson a major headache given his other defensive stalwart, Rio Ferdinand, is rarely able to string games together due to a series of muscular problems.

Ferdinand admitted last night United will face “ridicule” for dropping into the Europa League. In the past, United fans have taunted their Liverpool counterparts over Europa League participation by chanting “Thursday night, Channel Five”.

But Ferdinand insisted: “No matter what gets said, ridiculed or not, we respect the tournament and will go in there to win it.

“We are definitely good enough to bounce back,” he said.

“It is only a couple of weeks ago people were saying we were going to be champions and we were going to do this and that. It doesn’t change after one night in Europe.

“We have a lot of players here with valuable experience. That will come into play now.”

As if playing in the Europa League was not bad enough for United, they and Manchester City also face the prospect of having the second leg of their second-round ties rescheduled for a midweek afternoon.

Teams from the same city are banned from playing at home on the same day, which would mean United or City having to move their fixture to Tuesday or Wednesday, given that both clubs are seeded and will play their second legs at home.

But Uefa is also determined to prevent a Europa League match from clashing with a Champions League game.

With the possibility of extra time and penalties, the latest time at which a Europa League game could kick-off, if Uefa decides to enforce this convention, is 5pm.

It is the same fate that befell Everton two years ago when they had a clash with Liverpool and were eventually ordered to play Sporting Lisbon on the Tuesday, with a 5.45pm kick-off.